Physical adsorption of a gaseous species may change to chemical adsorption with ______________.

The basic difference between physical and chemical adsorption is that in the later case, a true chemical bond is formed between the adsorbent and the adsorbate. For this, chemisorption needs high temperature. But physisorption can occur at room temperature also.

So decreasing temperature cannot favor chemisorptions. So option (i) is wrong.

By increasing or decreasing the surface area of adsorbent it only changes the rate of physisorption. Therefore both (iii) and (iv) are wrong.

So, (ii) is the only correct option.